It happened that whatever problems others have, I also have them, and then some.
Maybe because of my non-standard (sophisicated I would say) setup, like all the partial encryptions, encrypted swap space, etc, reboot failed. I started the recovery mode. I got in, but what do I do?!
I tried to look at the boot log, no clue. And before that, the boot loader complained that all my NTFS (Windows) drives have fatal errors. That was real scary.
I tried to remove the last application that appeared at the boot log out of desperation. Then the first error message came out - that the software package manager wasn't in a proper state. I ran the suggested command and it was fixed. My computer manager to crash the software package manger at half the upgrade.
But that was fixed after wasting a lot of clueless time, swapping between the recovery mode, and normal mode a few times, and using the desktop to search for answers on the web.
Now the NTFS drives. Who haven't got one or two partitions? It's not safe to get rid of Windows altogether. I still can't see the ink levels on my printer.
It happened that they took out the fix NTFS utility from the system bundle. The system cannot find the programs to check and fix the NTFS drives, causing a fatal error. It is a valid philosophy, but stupid.
NTFS support is still there. You can mount the drive and read the data as before. Just that you cannot fix the hard disk errors. For that you have to download the newer optional NTFS package. But actually it is there and installed. But for some reason they call it another name, being new and different. You can also "fix" the disk errors from other utilities like the Disk Utilities.
I think the reason for the change is that the fix disk utilities is not as good as the Windows one. I fixed it on Ubuntu. But when I check it on Windows, it still got plenty of errors.
The proper solution is to edit the /etc/fstab file. For the NTFS disks, change the last 1 to 0, telling the system not to try checking and fixing them, using a package that didn't exist.
This is fixed after booting and fixing all the drives in Ubuntu and Linux, which is a waste of time. Like testing and fixing memory first, you should check and fix all your drives first, in Windows for NTFS, and others in Ubuntu, before you do major upgrade.
And of course you should backup your home directory first.
After successful booting, of course the default desktop environment is the new unity interface. The saving grace is that it's compatible with the classic Ubuntu gnome desktop, once again. The ridiculous fact is that 11.04 was not compatible with the earlier gnome desktop.
After I played around a bit, and maybe after some coding errors, unity disappeared. Everything seemed to be working. But I don't have the Unity to launch anything, and no system bar at the top. All I got is the bar for the "file explorer".
It happened that the desktop or whatever is called Compiz, and Unity is a plug-in. Somehow Unity is disappeared and you are left with a useless desktop, unless you have some application links on the desktop.
To reset to the default state of Compiz and Unity you need to do the following:
#gconftool-2 --recursive-unset /apps/compiz-1 #unity --reset
The tricky bit is that you can't start a terminal or anything. In recovery mode you also have to login as a normal user as the desktop settings is user specific. You can also try alt-ctrl-F1 that sort of thing to get a terminal to launch the commands.
Alt-ctrl-F1 gets you to the raw linux mode, without any GUI. It's like the recovery mode but with everything else normal, except the GUI. Alt-ctrl-t is the default hot key for bringing up a terminal.
Finally, after the hens and eggs problems, it worked. And now I can move to the new Unity because it beats Windows 7.
But I'm afraid there are problems at Ubuntu. Wrong philosophy? Many heads in all directions? Heading for the wrong path? These will be next.
ps It is recommended to install the Compiz settings manager but I advice against it until you sort out all your other troubles. It sets many other things so you can't go back to default even after you completely removes Compiz and reinstall.